Thread clamp for chain stitch sewing machines



2 Sheets-Sheet 1 R. K. HOHMANN THREAD CLAMP FOR CHAIN STITCH SEWING MACHINES A 0 J L Oct. 17, 1950 Filed 001-. 20, 1949 a M m T A Oct. 17, 1950 HOHMANN I 2,526,482

THREAD CLAMP FOR CHAIN STITCH sswms MACHINES Filed 0ce..- 20, 1949 'zsneets-sneet 2 IN V EN TOR. Rwy/1R0 I /OHMA/VN @01 aw w A 7'TORNfX Patented Oct. 17, 1950 THREAD CLAMP FOR CHAIN s'rrrcrr SEWING MACHINES Richard K. Hohmann, Jamaica, N. Y. Original application April 6, 1948, Serial No.

19,275. Divided and this application October 20, 1949, Serial N0. 122,388

2 Claims.

The general object of the present invention is to provide improved thread clamping mechanism for use in a chain stitch sewing machine to arrest and permit movement of the thread during predetermined portions of each stitch forming operation and characterized by its mechanical simplicity and operating characteristics.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

Of the drawings:

Fig. 1 is a sectional elevation of a sewing machine, the section being taken on the l-l line of Fig. 3;

Fig. 2 is a plan view of a portion of the machine shown in Fig. 1; and

Fig. 3 is an elevation in section on the of Fig. 1.

In the accompanying drawings, I have illustrated the use of the present invention, by way of example, in a light weight portable sewing machine whichis smaller in size than the conventional domestic sewing machine, and comprises a novel drive mechanism which is not claimed herein, but is claimed in my co-pending application, Serial No. 19,275, filed April 6, 1948, of which this application is a division. In the form shown, the frame of the sewing machine comprises a hollow base A open at its bottom, a hollow standard B extending upward from the base at one end of its work bed portion A, and a hollow arm portion C. Preferably and as shown, the base, standard and arm portions of the frame are integrall connected portions of a light weight metal casting. The frame metal is advantageously aluminum in the form known as hard aluminum. The arm portion C is formed with an opening C comprising a main portion extending along the entire upper side of the arm and depending portions at the front side of the needle head portion of the arm and at the opposite end of the arm. The opening C is normally closed by a detachable cover: plate C having a horizontal body portion and depending end portions C and C Screws may extend through the lower ends of the portions C and C to detachably secure the cover part to the-frame. An electric motor D is mounted in the hollow line 3-3 base of the sewingmachine frame and has its frame connected to the work bed portion of the base by screws D'. The base portion A is provided with a work bed extension A As shown, the motor shaft D carries a small pulley E which drives an intermediate pulley F through a belt G, ordinarily made of rubber. The pulley F is secured to an intermediate, or countershaft H which extends horizontally through the standard B at a level shown as about midway between the top side of the base Aand the underside of the arm C. The shaft H is journalled in integral internal boss portions B and B of the frame standard B. The boss 13 is carried by an integral web portion of the standard B. The pulley F is at the inner side of the sewing machine hand wheel F which is detachably clamped against the end of the hub of the pulley F by a clamping nut 1-1 on the threaded outer end of the shaft H. The hand wheel F has a portion which extends through a round opening in the adjacent wall of the standard B. 1

The shaft H is shown as connected through a sprocket chain belt I with the underbed hook shaft J of the sewing machine. At its front end,

the shaft J carries a hook J of a conventional chain stitch machine type. The belt I runs over a small sprocket wheel K carried by the shaft H and a larger sprocket wheel L carried by the shaft J at its rear end.

The sprocket wheel L serves as a crank disc carrying a crank pin L. The latter is connected by a link M to a pivot or crank pin N carried by a crank arm N secured to one end of an 05- cillating needle bar shaft N horizontally disposed in the sewing machine frame arm C.In

the desirable construction form shown, theshaft N is coaxial with and pivotally supported by trunnion pivots N which are secured, and: are axially adjustable in passages or openings formed in'web portions 0C and C of the arm C adjacent the opposite ends of the latter. The pivots 1W and the shaft N may be made of a suitable hard steel or steel alloy, and the pivots may bev large enough in cross-section to avoid any tendency, due to ordinary operating stresses, of the'pivots N to enlarge the openings in the portions of the aluminum frame arm C in which they are mounted. The use of the trunnion pivots W thus makes it unnecessary to mount bearing bushings in the aluminum frame for the shaft N.

The needle bar end of the shaft N carries a crank arm N connected through a link N to a pivot 'pin carried by a collar or pivot supporting an uprising portion S in horizontal threadedanchored. The post member which surrounds and is adjustably secured by a set screw 0 to the vertical needle bar 0. The latter is mounted in aligned openings formed in a thickened bottom wall portion (3 of the needle bar end of the arm C, and in an upper web portion 00 of the arm C. The needle bar 0 is provided at its lower end with means for the attachment to the bar of a needle 0 The up and down movement given the needle bar 0 is preferably greater than is customary in chain stitch machines, and is sufficient to permit the use of a needle 0 which is a commercially available, lock stitch type, sewing machine needle.

The needle bar 0 carries a second vertically adjustable collar member P above the member 0' which supports a vertical pin P parallel to and alongside the needle bar. The pin P is directly secured to the member P, and through the latter is connected to the needle bar 0, and is axially movable in an aligned passage formed in. the boss 00 and in the cover plate C between the similarly aligned sets of passages which respectively receive theupper portion of the needle bar 0 and the upper portion of the parallel presser bar Q; As is hereinafter described, the pin P; controls the operation of 'a thr ad clamp T. The presser bar is provided at its lower end with a presser foot Q, and is biased for down movement to hold the presser foot in engagement with the work. A presser bar lifting lever Q is mounted in the needle bar end of the arm C. The presser foot Q, lever Q and means biasing the presser bar for down movement may be conventional in form and arrangement.

The thread clam-p T, engaged by the pin P, is in the form of an elongated piece of sheet metal having its rear end clamped against the upper side of the body of a sheet metal support for thread tension discs R by the screw S. The latter extends through the clamp T and support S into the removable arm cover member C The other end of the spring T extends over the pin ,P secured to the metal bar 0. Adjacent its free end the clamp member is formed with a lateral thread clamping projection T which extends over a corresponding portion S of the support S. Except when the needle bar is in or near its uppermost position, the clamping projection T clamps the thread U against the part S As the needle bar approaches its uppermost position, however, the pin P engages the front end of the clamping member and raises the clamping projection T so as to permit the thread U to move freely in the direction of its length through the space between the part T and supporting The tension support S is formed with which one end of'a post or disc support R is R passes through and supports a pair of apertured tension discs R which frictionally engage the portion of the thread U passing between the discs. The tension with part S which the thread U is engaged by the discs is due to the action of the helical bias spring R The latter surrounds the post R and acts between the disc R remote from the supporting portion S and the adjustable abutment formed by a nut Rx threaded on the post R. As shown, the thread U passes to the tension discs R through a thread guide passage S formed in a transversely bent part of the uprising portion S of the member S. The thread passes to the passage S from a thread spool mounted on a spool support W secured to andextending upward from the cover plate (3 and including a thread guiding disc W larger in diameter than the spool and coaxial with the spool at the end of the latter adjacent the tension discs R:

The means for advancing the work over the work bed in the sewing operation comprises a feed bar X carrying a-feed dog X and formed at one end with an open ended slot X through which extends a horizontal supporting shaft X anchored in the frame base A. A spring X acting between the pin X and an abutment or feed bar shoulder X biases the feed bar for movement in a direction opposite to the direction of its feeding movement. At its end remote from the pin or post X the feed bar is bifurcated to form parallel leg portions X spaced away from one another by a distance equal to the diameter of a cam or eccentric disc Y secured to the hook shaft J between the hook J and adjacent end wall of the frame base A. The rotation of the member Y acts on the feed bar portions X to give the latter up and down movements, and acts against a curved bearing surface X extending between the legs X to give the feed bar moveduring the return stroke of-the feed bar.

The length of the feeding stroke is controlled by a stop lever Z pivotally connected to the sewing machine'frame base A-by a pivot pin Z and having a cam edge surface Z moved by the angular adjustment ofv the lever into, and is then frictionally held, in. a position in which it is engaged by an abutment portion X of the feed bar, earlier or later in each return movement of the feed bar under the action of the bias spring X The member X is advantageously in the form of a strip of spring metal having its ends attached by screws to the ends of the feed bar legs X. The spring strip X cushions the engagement of the feed bar with the stop lever Z. As shown, the feed dog X comprises two side by side horizontally elongated portions X withtheir upper edges serrated, which are received in slots formed in the work bed extension A During the feeding stroke of the feeding bar, the feed dog parts have their serrated upper edges above the level of the upper surface of the work b'ed extension. During the return or non-feed stroke of the feed bar, the serrated upper edges of the feed dog parts are lowered into the work bed extension slots.

The feed mechanism disclosed, but not claimed herein is claimed in my co-pending application, Serial No. 19,276, filed April 6, 1948, and novel features of the sewing machine frame disclosed, but not claimed herein, are claimed in my copending application, Serial No. 19,277, filed April 6, 1948. As will be apparent to those skilled in the art, however, the novel thread clamping mechanism claimed herein is not limited in use in sewing machines having any of the novel features disclosed by prior co-pending applications hereinbefore mentioned, but is adapted for use in chain stitch sewing machines of various other types and forms. While the particular sewing machine illustrated herein is smaller than the conventional domestic sewing machine, it is a practically operative machine, well adapted to do the work usually done on domestic sewing machines. As is specifically pointed out in said application, Serial No. 19,275, the sewing machine disclosed herein, is adapted to make about 750 together material varying in thickness from that of two plies or layers of fine silk fabrics to four plies or layers of heavy canvas.

While in accordance with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilledin the art'that' changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention, as set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A chain stitch sewing machine comprising in combination, a frame including a base portion forming a Work support and an elevated hollow arm portion extending over said hollow arm portion having a top portion with side-by-side first and second openings therein, a rotary hook mounted in said base portion, a reciprocating needle bar mounted in said arm portion and extending through said first opening and carrying a needle at its lower end, mechanism for rotating said hook and reciprocating said needle bar in timed relation to form chain stitches, a thread clam above and supported by said arm and comprising a clamping element extending over said second opening and biased for down movement into clamping engagement with the needle thread, and a clamp releasing part alongside said needle bar and connected to, a portion thereof within said hollow arm and arranged to move through said second opening and engage said clamping element and move the the work support,

latter to release the thread as the needle bar approaches the upper limit of its range of reciprocatory movement.

2. A chain stitch sewing machine comprising in combination, a frame including a base portion forming a work support and an elevated hollow arm portion extending over the work support,

, a rotary hook mounted in said base portion, a

reciprocatingneedle bar mounted in said arm portion and carrying a needle at its lower end for cooperation with said hook in the formation of chain stitches, mechanism for rotating said hook and reciprocating said needle bar in timed relation, said arm having upper and lower parts with an opening in each part through which the needle bar extends and in which it is longitudinally movable, said arm also having a second opening in said upper portion alongside and parallel to the first mentioned opening in said part, a pin alongside the needle bar and having its lower end connected tosaid needle bar and having its upper portion movably received in said second opening, a thread clamp above and supported by said arm and comprising a clamping part biased for down movement into clamping engagement with the thread, and comprising a clamp releasing part extending over said second opening, said pin being arranged to engage said releasing part and thereby move said clamping part to release the thread as the needle bar approaches the upper limit of its range of reciprocatory movement.

RICHARD K. HOHMANN.

Number Date Fitzgerald et al. Jan. 8, 1884 

